U.S. patent number 4,745,690 [Application Number 07/002,079] was granted by the patent office on 1988-05-24 for method of replenishing and/or preparing treating liquids.
This patent grant is currently assigned to Polygram International Holding B.V.. Invention is credited to Hermann Koop, Friedrich-Wilhelm A. Thein.
United States Patent |
4,745,690 |
Koop , et al. |
May 24, 1988 |
Method of replenishing and/or preparing treating liquids
Abstract
The invention relates to a method of replenishing and/or
preparing water-displacing treating liquids or mixtures of these
treating liquids and of water-absorbing liquids. Said liquids are
contained in treating compartments and are used to remove water
which adheres to the surface of objects immersed in the treating
liquids. The objects may consist of, for example, glass, ceramic,
nickel, copper, stainless steel or synthetic resin such as, for
example, disc-shaped information carriers.
Inventors: |
Koop; Hermann (Ronnenberg,
DE), Thein; Friedrich-Wilhelm A. (Wunstorf,
DE) |
Assignee: |
Polygram International Holding
B.V. (Baarn, NL)
|
Family
ID: |
6291769 |
Appl.
No.: |
07/002,079 |
Filed: |
January 12, 1987 |
Foreign Application Priority Data
|
|
|
|
|
Jan 14, 1986 [DE] |
|
|
3600778 |
|
Current U.S.
Class: |
34/340; 34/473;
34/78; G9B/23.098 |
Current CPC
Class: |
B01D
3/00 (20130101); G11B 23/505 (20130101); C23G
5/02 (20130101); B01D 12/00 (20130101) |
Current International
Class: |
B01D
12/00 (20060101); B01D 3/00 (20060101); C23G
5/02 (20060101); C23G 5/00 (20060101); G11B
23/50 (20060101); F26B 005/16 () |
Field of
Search: |
;34/9,75,78,60,27,32 |
References Cited
[Referenced By]
U.S. Patent Documents
Primary Examiner: Schwartz; Larry I.
Attorney, Agent or Firm: Spain; Norman N.
Claims
What is claimed is:
1. A method of replenishing and/or providing water-displacing
treating liquids or mixtures of said treating liquids and of
water-absorbing liquids in treating compartments, which liquids are
used to remove water from the surfaces of objects to be immersed in
the treating liquids, said objects being made of glass, ceramic,
nickel, copper, stainless steel or synthetic resin such as, for
example, disc-shaped information carriers, characterized in that
the surfaces of the treating liquids in the compartments are kept
at such a temperature that a similar, vaporized treating liquid
which is provided over said surfaces condenses on said
surfaces.
2. A method as claimed in claim 1, characterized in that the
vaporous treating liquid which condenses on the surfaces is
vaporized by heating in a vaporization compartment.
3. A method as claimed in claim 1, characterized in that a mixture
of a fluorocarbon and an alcohol is used as a treating liquid.
4. A method as claimed in claim 1, characterized in that the
treating liquids in the treating compartments are kept at a
temperature below their vaporization temperature.
5. A method as claimed in claim 3, characterized in that the
mixture of fluorocarbon and alcohol in the treating compartment is
kept at a temperature which is from 7.degree. to 15.degree. C.
below the boiling point of the mixture.
6. A method as claimed in claim 2, characterized in that the fluid
fluorocarbon-alcohol mixture in the vaporization compartment, which
is to be vaporized by heating, has such an alcohol concentration
that the vaporous treating liquids and the treating liquids which
are in the treating compartments are azeotropic or of a similar
composition.
7. A method as claimed in claim 1, characterized in that water
and/or water-contaminated treating liquid are/is led from the
surfaces of the treating liquid in the treating compartments to at
least one water separator by means of overflow devices, after which
they/it are/is supplied to a storage tank from where they/it are/is
pumped through a filter and vaporized in the vaporization
compartment.
8. A method as claimed in claim 1, characterized in that the
vaporized treating liquid is also used to rinse the condensate off
an object lifted from a treating compartment.
9. A method as claimed in claim 1, characterized in that the
vaporized treating liquid is contained in a bounded space which
comprises a cold trap from where the condensed, water-contaminated
treating liquid is supplied to a water separator and then passed on
to at least one treating compartment.
10. A method as claimed in claim 7, characterized in that the
treating liquid is cooled in the water separator(s), thereby
obtaining the desired temperatures of the treating liquids in the
treating compartments.
11. A method as claimed in claim 9, characterized in that the
treating liquid is cooled in the water separator, thereby obtaining
the desired temperatures of the treating liquids in the treating
compartments.
12. A method of replenishing and/or providing water-displacing
treating liquids or mixtures of said treating liquids and of
water-absorbing liquids in treating compartments, which liquids are
used to remove water from the surfaces of objects to be immersed in
the treating liquids, characterized in that the surfaces of the
treating liquids in the compartments are kept at such a temperature
that a similar, vaporized treating liquid which is provided over
said surface of the treating liquids condenses on said surfaces.
Description
BACKGROUND OF THE INVENTION
The invention relates to a method of replenishing and/or providing
water-displacing treating liquids or mixtures of these treating
liquids and of water-absorbing liquids in treating compartments,
which liquids are used to remove water from the surfaces of objects
to be immersed in the treating liquids, said objects being made of
glass, ceramic, nickel, copper, stainless steel or synthetic resin
such as, for example, disc-shaped information carriers.
In the art there is a need for methods of removing liquids from
objects whose surfaces are contaminated by said liquids. In the
case of, for example, optically-readable disc-shaped information
carriers such as, compact-discs the water used to clean them must
be removed after the cleaning process. The same applies to silicon
discs and copper and glass components which are used in electric
circuits. When such objects are dried it is important that no
deposition residues are left behind on their surfaces in the form
of drying spots. Moreover, to avoid mechanical attack of the
objects to be dried, it is to be noted that in the drying process
certain predetermined temperatures are not to be exceeded. When
drying, for example, disc-shaped information carriers such as, for
example, compact discs, a temperature of 90.degree. C. must not be
exceeded. A further important factor in drying is that the objects
to be dried are not contaminated by particles which are suspended
in the treating liquid. Consequently, high-grade, i.e. highly pure,
treating liquids must be used.
DE-OS No. 23 01 357 describes a method and an arrangement for
removing liquids from solid surfaces, according to which method an
object having a surface which is contaminated by a liquid is
immersed in a solvent-containing bath, the density of the solvent
being different from that of the liquid. The solvent is agitated,
thereby removing the liquid from the object. The liquid and the
solvent are discharged from the bath and after the solvent has been
separated from the liquid it is fed back to the solvent-containing
bath. This method requires a very pure solvent which is very
expensive. Moreover, when high demands are imposed upon the purity
of the solvent it must be refreshed very frequently, thereby
rendering uneconomical this method of removing liquids.
DE-OS No. 31 25 980 describes a method of manufacturing carriers
having a high information density, in which surface impurities are
first removed by an aqueous rinsing agent which is subsequently
removed by rinsing the carriers with a liquid fluorocarbon. Next,
the carrier is maintained in a fluorocarbon vapour until the
carrier temperature equals the vapour temperature. Also in this
method the liquid fluorocarbon must be very pure, and as it is
contaminated in the disc-rinsing process it must be frequently
refreshed.
It is an object of the invention to provide a method of
replenishing and/or providing water-displacing or water-absorbing
treating liquids, which allows for an efficient use of solvents so
that the preparing and replenishing of absolutely pure treating
liquids can be dispensed with.
This object is achieved according to the invention, by a method in
which the surfaces of the treating liquids in the compartments are
kept at such a temperature that a similar, vaporized treating
liquid which is provided over these surfaces condenses on those
surfaces.
Such a method of replenishing and/or providing water-displacing or
water-absorbing treating liquids or mixtures thereof has the
advantage that the treating liquids present in the liquid phase in
treating compartments can be replenished continuously with a
similar liquid which is provided in the vapor phase and which
condenses on the surfaces of the liquid phase treating liquids in
the treating compartments.
As the treating liquids are first vaporized and are not used as a
treating liquid until they have condensed, an inevitable
purification of the treating liquids takes place because due to the
vaporization they cannot entrain the solid contaminations. This is
advantageous, both in filling the treating compartments, i.e. when
they are filled for the first time, and in the continuous
regeneration of the liquids in the treating compartments. In order
to continuously regenerate the treating liquids in the treating
compartments, these liquids are discharged from the treating
compartments, vaporized and condensed again on the surfaces of the
liquid in these compartments. In this way the treating liquids are
continuously subjected to a process in which they are vaporized
and, thus, purified and cleared of water. Thus, this method is
economically feasible and, moreover, provides a highly pure
treating liquid.
This method can be applied to water-displacing treating liquids,
mixtures thereof and water-absorbing liquids.
The selection of the temperatures of the treating liquids in the
treating compartments depends on the composition of these liquids
and on the material and properties of the objects to be treated. In
any case, the temperature of the treating liquids in the
compartments must be kept below the vaporization temperature of the
liquids if a vaporized similar treating liquid which is situated
above the surfaces of the treating liquids is to condense on these
surfaces.
In accordance with a further embodiment of the inventive method,
the vaporous treating liquid which condenses on these surfaces is
vaporized by heating in a vaporization compartment.
In a vaporization compartment the treating liquids can readily be
vaporized by heating. Consequently, both treating liquids which are
discharged from the treating compartments and fresh, unused
treating liquids can be supplied to said vaporization compartment.
The vaporization compartment must be arranged so that the vaporized
treating liquid is supplied to the surfaces of the treating liquids
in the treating compartments where the vapour will then
condense.
According to a further embodiment of the inventive method, a
mixture of a fluorocarbon and an alcohol is used as a treating
liquid. An exmple of a suitable fluorocarbon is
1,1,2-trichloro-1,1,2-trifluoro-ethane.
If water is to be removed from the surfaces of the objects to be
treated, a liquid fluorocarbon is a suitable treating liquid
because its specific gravity is higher than that of water and it
removes the water from the surfaces of the objects to be treated.
When the alcohol is added to the fluorocarbon, the removal of
moisture from the surfaces of the objects to be treated is
facilitated because alcohol absorbs water. Suitable alcohols are,
for example, isopropanol, methanol, ethanol and butanol.
According to a further embodiment of the method of the invention,
the mixture of the fluorocarbon and alcohol in the treating
compartments is kept at a temperature which is from 7.degree. C. to
15.degree. C. below the boiling point of the mixture.
Advantageously, this temperature range is observed because on the
one hand the temperature of the water in the ambient air does not
fall below the dew point, and thus the formation of a water film on
the liquid mixture in the treating compartments is avoided, and on
the other the temperature is seleted so that the vaporized treating
liquid above the compartments condenses on the fluid treating
liquids in the compartments. Moreover, in order to ensure an
adequate replacement of the treating liquid in the compartments,
the temperature of the treating liquids in the treating
compartments must be selected so that a sufficient quantity of the
vaporized treating liquid condenses on the surfaces.
According to a further embodiment of the invention, the alcohol
concentration of the liquid fluorocarbon-alcohol mixture in the
vaporization compartment, which mixture is to be vaporized by
applying heat, is such that the vaporous treating liquids and the
treating liquids which are in the treating compartments are
azeotropic or of a similar composition. In order to ensure that the
mixture in the treating compartments is azeotropic, the alcohol
concentration in the vaporization compartment must at least be
sufficient so that the mixture is azeotropic. An upper limit is set
to the alcohol concentration in the vaporization compartment by the
fact that the fluorocarbon-alcohol mixture should be free of
inflammable vapors. Thus, the alcohol concentration generally lies
between 1.5 and 15% by weight.
According to a further embodiment of the invention, water and/or
water-contaminated treating liquid are/is led from the surfaces of
the treating liquid in the treating compartments to at least one
water separator by means of overflow devices, after which they/it
are/is supplied to a storage tank, from where they/it are/is pumped
through a filter and vaporized in the vaporization compartment.
As the water or the water-contaminated treating liquid has a lower
specific gravity than the uncontaminated treating liquid, the water
or the water-contaminated treating liquid accumulates at the
surface of the liquids in the treating compartments. Subsequently,
overflow devices supply the water to a known water separator which
operates according to the principle of gravity. The treating liquid
is then led into a storage tank which is designed so that the
treating liquid used in the process does not have to be replaced
continuously but rather at irregular intervals. From the storage
tank the treating liquid is pumped through a filter in which it is
purified mechanically. After filtering the liquid flows into an
arrangement in which it is vaporized again.
According to a further embodiment of the invention, the vaporized
treating liquid is also used for rinsing the condensate off an
object which is pulled out of a treating liquid in treating
compartment.
As the temperature of the fluid treating liquid in the treating
compartments is below the vaporization temperature, the vaporized
treating liquid can also be used for rinsing a condensate. If an
object is pulled out of the treating liquid in the treating
compartment after it has been immersed therein for a sufficiently
long time, its temperature will be substantially equal to that of
the fluid treating liquid, i.e. a temperature below the
vaporization temperature. Consequently, after the object has been
pulled out the vaporized treating liquid will deposit as a
condensate on the surface of the object and rinse it. Thus, the
vaporous treating liquid is used twice, namely on the one hand to
replenish the liquids in the treating compartments and on the other
to rinse the condensate off the objects which are pulled out of the
liquids in the compartments.
According to a further embodiment of the invention, the vaporized
treating liquid is contained in a bounded space in the upper part
of which there is a cold trap from where the condensed,
water-contaminated treating liquid is led to a water separator and
subsequently passed on to a treating compartment.
The space above the treating compartment, in which vaporized
treating liquids are present, is essentially closed, although it
must have an aperture to enable objects to be supplied to or
withdrawn from said space. To separate said aperture from the
vapour present in the space, a cold trap is provided in the
vicinity of the aperture, on which both the vapour of the treating
liquid and the water vapour condense. The treating liquid is
separated from the condensed water in a water separator. The
treating liquid is then again supplied directly to the treating
compartments or to the storage compartment.
According to a further embodiment of the inventive method, the
treating liquid is cooled in the water separator(s), thereby
obtaining the desired temperatures of the treating liquids in the
treating compartments. The cooling of the treating liquids has the
additional advantage that the water can be separated more
readily.
An exemplary embodiment of the invention will now be explained in
more detail with reference to the drawings, in which
FIG. 1 is a sectional view of a drying arrangement which operates
according to the inventive method,
FIG. 2 is a sectional view along the line II--II of the arrangement
according to FIG. 1.
In FIG. 1 an arrangement for drying disc-shaped information
carriers (compact discs) is shown in section, which operates
according to the method of refilling and/or providing
water-displacing treating liquids in treating components.
As shown in FIG. 1 in the arrangement 1 a first treating
compartment 2 and a second treating compartment 3 are arranged next
to one another. A vaporization compartment 4 is arranged next to
the second treating compartment 3. A storage tank 5 is arranged
next to the first treating compartment 2. The storage tank 5
includes a filling tube 6 and an inlet tube 7. The filling tube 6
and the inlet tube 7 lead to a water separator 8 which is arranged
in the storage tank 5. The water separator 8 operates according to
the principle of gravity, i.e. as the water is lighter than the
treating liquid it will deposit on top of this liquid after which
it is carried away in a way not shown in the drawing. Treating
liquid which is cleared of water is led away from the water
separator through an aperture 9, which is arranged at the bottom of
the storage tank, and is then supplied to a further water separator
10. Via an aperture 11 in the water separator 10, treating liquid
flows between partitions 12 and 12a and via a discharge aperture 13
into a storage compartment 14. In the storage compartment 14 there
is a water-cleared treating liquid 15. A pipe 20 is arranged in the
lower part of the storage compartment 14, by means of which
treating liquid is discharged from the storage compartment. In the
pipe 20 the treating liquid is first led through a flow control
element 21 by means of which the rate of flow can be controlled.
Next, the treating liquid is pumped through a filter 23 by a pump
22. The filter 23 is a mechanical one and it is used to retain any
solid particles still present in the treating liquid. Behind the
filter 23 a pipe 24 leads to a discharge aperture 25 which is
provided above the vaporization compartment 4, so that treating
liquids emanating from the aperture 25 flow into the vaporization
compartment 4. A further pipe 26 having a flow control element 27
for controlling the rate of flow extends from the filter 23 to an
overflow arrangement 30. The overflow arrangement 30 is arranged in
the upper part of the treating compartment 2, such that it is in
the vicinity of the surface of a fluid treating liquid 31 in the
treating compartment 2. The overflow arrangement 30 operates as
follows: the liquid pumped into the overflow arrangement 30 via the
pipe 23 is driven over the surface of the treating liquid 31 in the
compartment 2, so that the water or water-contaminated treating
liquid present on the surface of the treating liquid flows over an
overflow edge 32 at the other side of the treating compartment 2
into the inlet tube 7 of the storage tank 5 from where it flows
into the water separator 8. The flow control element 27 in the pipe
26 can be adjusted so that as much as possible of the water
supplied to the surface of the treating liquid in the treating
compartment 2 by the overflow arrangement so as to be led into the
storage tank 5 via the overflow edge 32.
By means of a pump 22 the treating liquid is led through the pipe
24 and the discharge aperture 25 into the vaporization compartment
4, in a lower part of which it accumulates. Heating tubes 35 are
provided below the bottom 34 of the vaporization compartment, which
tubes are used to indirectly heat the fluid treating liquid in the
treating compartment until it vaporizes. The heating tubes 35 may
be of different construction; the heating capacity must however be
such that the treating liquid in the treating compartment 4 is
vaporized. Above the treating compartments 2 and 3 and the
vaporization compartment 4, which are arranged next to each other,
there is a space 42 which is bounded at the sides by walls 40 and
41. At the top, the space 42 is bounded by a cold trap 43.
FIG. 2 is a sectional view along the line II--II of the treating
compartment 3, the space 42 and the cold trap 43. A treating liquid
45 in the treating compartment 3 is led through an aperture 47 in
the bottom part 46 of the compartment and through a flow control
element 48 after which it is pumped through a filter 50 by means of
a pump 49. The filter has the same function as the filter 23,
namely the removal of solid particles. Behind said filter 50 the
treating liquid is led to an overflow device 52 by a pipe 51. The
overflow device operates in the same way as the overflow device 30
of the treating compartment 2. The contaminated treating liquid
which is pumped over the surface by means of the overflow device 52
is supplied to a water separator 55 via an overflow edge 54, the
separator being located on the other side 53 of the compartment,
opposite the outflow arrangement. The water separator 55 operates
in the same way as the water separator 8 of the storage tank 5.
Treating liquid which is cleared of water is supplied (in a manner
not shown) from the bottom 56 of the water separator 55 to the
vaporization compartment 4 of FIG. 1 via a pipe 57. The aqueous
phase of the treating liquid which is separated in the water
separator is supplied to the water separator 8.
The expansion of the vapour of a treating liquid present in the
space 42 is bounded at the upper side by a cold trap 43 which is
arranged at the side 60 of an upper aperture 62 in said space 42.
The vapour or watr vapour condensing in the cold trap 43 is
supplied to a water separator 62 which in accordance with the water
separators 56 and 8 operates according to the principle of gravity.
A treating liquid which is cleared of water and which is discharged
from the bottom 63 of the water separator 62 is supplied to a tank
65 via a pipe 64. The tank 65 is used for intermediate storage. The
fluid treating liquid in the tank 65 is discharged via the bottom
of the tank and led through a pipe 66 to a treating compartment 3.
Via an aperture 67 in the bottom of treating compartment 3 the
treating liquid is introduced into said treating compartment where
it is added to the treating liquid 45 already present.
The arrangement shown in FIGS. 1 and 2 operates according to the
method of replenishing and/or preparing treating liquids as will be
described below. The treating liquid which is vaporized in the
vaporization compartment 4 accumulates in the space 42 above the
treating compartments 2 and 3 and vaporization compartment 4. The
cold trap forms the upper boundary of the vapour in said space 42.
The fluid treating liquids 31 and 45 in the treating compartments 2
and 3 exhibit a temperature which is below their vaporization
point. Consequently, the vapour of the same liquid, which is
present above the compartments 2 and 3, condenses on the surfaces
of the fluid treating liquids 31 and 45 in the compartments 2 and
3. By means of the overflow devices 30 and 52 the surfaces of the
liquids in the compartments 2 and 3, respectively, are cleared of
water or water-contaminated treating liquid which enters the
compartments through the objects immersed therein. The treating
liquid which is cleared of water in the water separator 52 is
supplied to the vaporization compartment 4 and the separated
aqueous phase is supplied to the water separator 8. The treating
liquid which is carried away by the overflow device 30 and which is
cleared of water is led to the storage tank 5. Subsequently, the
treating liquid is again supplied to the overflow device 30 or to
the vaporization compartment 4 where the treating liquid is
vaporized again, after which it condenses on the surfaces of the
treating liquids 31 and 45 in the compartments 2 and 3.
In this way the treating liquid is subjected to a cyclic process in
which the treating liquid is vaporized time and again in the
vaporization compartment 4 after which it condenses on the surface
of the fluid treating liquid 31 or 45. Consequently, the treating
liquid is vaporized time after time and, thus, purified. By this
process, both the treating liquid which is to be replenished and
the fresh treating liquid which is introduced via the tube 6 of the
storage tank 5 are purified in the same way, because they are led
to the vaporization compartment 4 where they are vaporized via the
storage tank and the filter 23. The treating liquid does not
contact the objects to be dried until it has condensed again. Even
when high demands are put on the purity of the treating liquid in
the compartments 2 and 3, the treating liquid used to fill the
arrangement for the first time does not have to meet these
requirements. In this case, the arrangement is filled with the
treating liquid and is operated in an idle condition, i.e. a
condition in which the vapour which is vaporized in the
vaporization compartment 4 condenses on the surfaces of the
treating liquids 31 and 35 in the treating compartments 2 and 3,
until the treating liquid in the compartments 2 and 3 have been
sufficiently purified. Moreover, although the treating liquid is
contaminated over and again by immersed objects when the
arrangement is in operation, it has to be refreshed relatively
rarely because it is purified over and again by the cyclic
conversion into the vapor phase.
A mixture of fluorocarbon and isopropanol has proved to be a
suitable treating liquid. Although the alcohol concentration of the
fluid mixture in the compartment 4 is of secondary importance, it
must be selected so that the vapor of the mixture and the condensed
mixture in the compartments 2 and 3 are azeotropic. Experience has
shown that an azeotropic concentration of the mixture is sufficient
to dry objects in the compartments 2 and 3. To dry the objects they
are first immersed in the fluid treating liquid 31 in the
compartment 2. After the objects have been immersed in the liquid,
a large part of the water adhering to the objects rises to the
surface where an overflow device 30 feeds the water via the
overflow 32 to the water separator 8 in the storage tank 5. The
water rises to the surface of the treating mixture 31 in the
compartment, because the latter has a higher specific gravity than
water. Furthermore, the alcohol contained in the mixture absorbs
any water residue still adhering to the objects, and owing to the
smaller specific gravity of water in comparison with the treating
liquid the former rises to the surface where it is discharged by an
overflow device 30 via an overflow 32. In order to remove any
moisture still adhering to the objects, ultrasonic generators 70
and 71 may be arranged on two opposed sides 67 and 68 of the
treating compartment 2, which generators are not put into operation
until the greater part of the water has reached the surface and has
been removed by an overflow device 30. After the ultrasonic
generator has been put into operation some more water or residual
moisture becomes detached from the objects due to the turbulence of
the treating liquid, and is also removed from the surface of the
treating liquid. After as much as possible of said residual
moisture has been removed from the surfaces of the objects not
shown in the drawing, the object is lifted from the treating
compartment 2 and is led into the space 42 which is filled with
vapour of the treating liquid. As the object has substantially
adopted the temperature of the fluid treating liquid in the
treating compartment 2, its temperature is at least several degrees
below that of the vapour of the treating liquid in the space 42.
Consequently, this vapour condenses on the surfaces of the object.
In this way, the object is again rinsed with the treating liquid.
Subsequently, the object is immersed in the treating liquid 45 in
the second treating compartment 3. In the treating compartment 3,
the object is cleared of any residual water in the same way as in
compartment 2, yet more thoroughly because treating compartment 3
only contains objects with very little residual moisture,
consequently, the fluid treating liquid 45 in the treating
compartment 3 is only slightly contaminated by water. After the
object is introduced into the treating liquid 45 in the treating
compartment 3 and is cleared of any remaining residual moisture, it
is pulled out of the fluid and led into the space 42. As the
temperature of the fluid treating mixture 45 in the compartment 3
is at least a few degrees below that of the vapor of the mixture in
space 42, said vapor condenses on the surface of the object when
the object is lifted from the compartment 3. In this way the
condensate is rinsed again. Subsequently, the object is slowly
moved upward in the space 42. In this process, the object is heated
until it has almost attained the temperature of the vapor and
hardly any vapour condenses on its surfaces. The object is slowly
dried and is carried past the cold trap 43 through the aperture 61
into the ambient air. In this way the object is dried so that it is
free from any residue, i.e. without any drying spots. The retention
time of the object to be dried in the treating compartments or in
the vapour depends upon the temperatures selected and on the heat
capacity of the object. The retention time is longer as the heat
capacity of the object is higher.
* * * * *